For a car whose fate was anything but certain at the outset, the Porsche 911 Carrera RS 2.7 has been more than vindicated.

A runaway success commercially and competitively, this groundbreaking variant of the 911 would unwittingly form the very bedrock of Porsche’s engineering and corporate strategy since debuting in 1973 during a period of internal upheaval as the German automaker restructured its production and motorsports programs.

Indeed, the close kinship between Porsche’s roadgoing and competition models—now a Porsche hallmark—is largely thanks to the 911 RS 2.7, which was developed in the early Seventies for Fédération Internationale de l'Automobile Group 4 competition, which required 500 streel-legal examples for homologation.

Hard to fathom given the RS 2.7’s present popularity, Porsche marketing execs had little faith at the time that the company could sell more than 80 examples to private racers.

“Considering the extremely spartan equipment necessitated by weight requirem...